A long-delayed audit of California's troubled regulation of natural-gas utilities - called for by a state blue-ribbon panel after the 2010 San Bruno pipeline explosion and only recently begun - is back on hold for at least six months because of a technicality in state contracting rules.

The utilities commission was criticized in a subsequent report on the explosion by the National Transportation Safety Board, which said the state had taken an excessively hands-off approach toward the San Bruno pipeline's owner, Pacific Gas and Electric Co.

It took a year for the utilities commission to approve the $260,000 audit by NewPoint Group Inc., a consultant outfit in Sacramento that finally started the review in August. But after NewPoint was purchased by Crowe Horwath LLP in September, the utilities commission ordered the review halted.

"As (Crowe Horwath) was not the selected bidder, we must now reissue the (request for bidding proposals), per state contracting rules," the commission said in a statement.

That could take another six months, pushing the audit well into next year. Commission officials say they hope to expedite the process.

The audit is expected to address what the National Transportation Safety Board called "fundamental problems" with the utilities commission's regulation of PG&E.

The safety board's report on the Sept. 9, 2010, San Bruno disaster said the commission's "culture serves as an impediment to effective regulation." It also said the state agency lacked the resources and "the organizational focus" to regulate PG&E well.

The federal report laid primary blame for the explosion on PG&E, saying it had installed a flawed pipe in San Bruno in 1956 and never had an inspection system that would have detected the problem. The safety board's chairwoman said PG&E had "exploited weaknesses in a lax system of oversight."

Assemblyman Jerry Hill, D-San Mateo, whose district includes the neighborhood where eight people were killed and 38 homes destroyed in the blast, said the audit's delay endangers public safety.

"We can't wait another six months for this - wait for another San Bruno-like incident in California - to take immediate action," Hill said. "This is critical work."

Tom Long of The Utility Reform Network, a group that advocates for utility customers, said the audit "will be important in assuring the public that our regulators are doing the job they need to do. It would be good to get this audit under way as soon as possible."